Function Keys (Fn) not working

I recently performed a full system restore on my Inspiron 3580 after certain software+hardware issues made it unavoidable, and I afterwards downloaded SupportAssist and downloaded the required drivers to have the laptop running as it did before. However my issue comes in that the Function 'fn' key does not work at all. The normal F1-F12 keys all work as normal, but I cant use the fn key to toggle brightness, volume, etc, which is something of a problem as I had begun to rely on that quite alot. Any suggestions on what I should do to get it running again as it used to?